A mutating table error occurs when a table is modified in a way that violates its schema. This can happen when a user attempts to insert a value into a column that has a different data type than the column is defined to have, or when a user attempts to update a value in a column that is defined as read-only.
There are several ways to avoid mutating table errors. One way is to use the correct data types when inserting or updating data. Another way is to use the appropriate INSERT and UPDATE statements. Finally, it is important to test all code that modifies data to ensure that it does not cause mutating table errors.